Talk about power -- a polar bear could beat many of the greatest human athletes. On land, a polar bear can run as fast as 25 mph (40 kph) for short distances. In water, they’ve been tracked swimming continuously for 62 miles (100 km). Open your hand–a newborn polar bear would likely fit in it. Yet that cub will grow to become one of the largest land predators alive today. Adult females can weigh around 500 lb. (227 kg)–hefty males can be three times as heavy!